Background: Nutrition in pregnancy has important implications for both the mother and the fetus, hence the importance of an accurate assessment at the booking visit. Body mass index is currently the gold standard for measuring body fatness. However, pregnancy associated weight gain and oedema, as well as late booking in our population setting, questions the reliability of using the BMI to assess body fat or nutritional state in pregnancy. Mid upper arm circumference has been used for many decades in children under the age of five, to assess malnutrition. Many studies have shown a strong correlation between MUAC and BMI in the adult population. MUAC is a much simpler anthropometric measure to take as it eliminates the need for height charts, scales and calculations. One of the other main advantages of using MUAC is that there is minimal change in the MUAC during pregnancy, which may be a better indicator of pre-pregnancy body fat and nutrition. Objectives: To assess if there is a correlation between the mid upper arm circumference and body mass index in pregnant woman booking in the Metro West area. Methods: This was a cross sectional study of women booking at four MOUs in the Metro West area. Anthropometric measurements namely height, weight and MUAC were carried out on pregnant women booking for the first time in four midwives obstetrics units in Metro West area, Cape Town, South Africa. The participants were divided into two groups, early gestational age group for patients who booked less than twenty weeks, and a late gestational age group for those who booked more than twenty but less than thirty week Results: The results showed that there is a strong correlation between MUAC and BMI in pregnant women up to thirty weeks gestation. The correlation was calculated at 0.92 for the entire group. A regression analysis showed that there is a statistical difference in the mathematical relationship between BMI and MUAC, between the two groups (EGG and LGG). MUAC of 27cm and 31cm had sensitivities and specificities of more than 80% for identifying pregnant women as overweight and obese respectively. Conclusion: The MUAC correlates strongly with BMI in pregnancy up to a gestation of thirty weeks in women in Metro West maternity services. In a low resource settings, the simpler MUAC measurement to assess nutritional status and screen women who are at risk for potential adverse pregnancy outcomes could reliably be substituted for BMI estimation.